I really enjoyed reading Richard Mabey's Food For Free whilst curled up in my favourite armchair. It is organised season-by-season so you can see what is potentially available at any time of year. I flicked straight to the "autumn" section to see what is available now, although some things are available for more than one season - dandelions, for example, and some kinds of mushrooms. Other plants offer different things at different times of year. Elder trees, for example, are listed under Spring, because the flowers can be picked then, but not under Summer when the berries ripen.
There are lots of full colour photos, but many of them are not large enough or clear enough to allow you to identify the plant (or fungus etc.) if you are not already familiar with it. It should show you clear illustrations of the leaves, the flowers and the fruit. I don't think it would be a very practical field guide, but I don't think it is trying to be - it is too large a book anyway. So you'll still need a fungus field guide, a tree guide and a wildflower/plant field guide to figure out exactly what to pick.
Food for Free contains some recipes, but it's not really a cookery book either. For one thing, I wouldn't want to splash ingredients or scribble recipe adjustments on its lovely pages (I tend to abuse my recipe books somewhat) and there is no separate recipe index. It doesn't seem to want to open flat either, an essential quality in a cookbook if you ask me.
I sound like I'm coming down quite hard on it, but I don't mean to. The book has many great features. For example, it is very extensive, covering not only the widespread and bountiful forage such as dandelion leaves and blackberries, but also rare things such as truffles and early purple orchids.
I notice that there is a Collins Gem version. I wonder how it differs from the large lavish paperback version I've got? Because I think what's really needed is 3 different books - a field guide to edible wild plants and fungus, a cookbook for them, and an armchair book. This is the armchair version. Now where are the other two?